A brace from Mark Farren ensured Derry City secured maximum points at Mervue United and opened up a seven point lead at the top of the table.
The visitors broke the deadlock on 21 minutes following a super flowing move, which ended with David McDaid’s pass releasing Farren, and the striker made no mistake from 12 yards, firing past Ger Hanley.
Stephen Kenny’s side had to make a change soon after when Deery limped off to be replaced by Ruairi Harkin.
That change didn’t seem to disrupt the Brandywell men as a Harkin corner on 33 minutes found Mark Scoltock and his knock down fell to James McClean, but his drive was blocked on the line.
The Candystripes had a good chance to double their lead on 73 minutes when Patrick McEleney’s through ball released Farren, but his shot on the edge of the box whistled just over.
The decisive second goal came eight minutes from time when Shane McEleney won possession before playing a super long ball down field for Farren, who easily rounded the out-rushing, and side-footed home.
The home side scored a consolation goal in stoppage time when substitute Rory Gaffney turned the ball home from close range.
Mervue United: Hanley, Walsh, Farrell, Elwood, N Curran; Walsh, Tierney, Cunningham, Crehan, Connolly; Hoban. Subs: Gaffney for Connolly (63); Ludden for Cunningham (72); Goldbey for Farrell (79).
Derry City: Doherty, McCallion, S McEleney, Scoltock, Friars; P McEleney, McBride, Deery, McClean; McDaid, Farren. Subs: Harkin for Deery (25); McChrystal for McDaid (H-T); Coyle for P McEleney (90).
Referee: Padraigh Sutton (Clare).